/*
 * jccolor.c
 *
 * Copyright (C) 1991-1994, Thomas G. Lane.
 * This file is part of the Independent JPEG Group's software.
 * For conditions of distribution and use, see the accompanying README file.
 *
 * This file contains input colorspace conversion routines.
 */

#define JPEG_INTERNALS
#include "jinclude.h"
#include "jpeglib.h"


/* Private subobject */

typedef struct
{
	struct jpeg_color_converter pub;	/* public fields */

	/* Private state for RGB->YCC conversion */
	INT32          *rgb_ycc_tab;	/* => table for RGB to YCbCr conversion */
} my_color_converter;

typedef my_color_converter *my_cconvert_ptr;


/**************** RGB -> YCbCr conversion: most common case **************/

/*
 * YCbCr is defined per CCIR 601-1, except that Cb and Cr are
 * normalized to the range 0..MAXJSAMPLE rather than -0.5 .. 0.5.
 * The conversion equations to be implemented are therefore
 *	Y  =  0.29900 * R + 0.58700 * G + 0.11400 * B
 *	Cb = -0.16874 * R - 0.33126 * G + 0.50000 * B  + CENTERJSAMPLE
 *	Cr =  0.50000 * R - 0.41869 * G - 0.08131 * B  + CENTERJSAMPLE
 * (These numbers are derived from TIFF 6.0 section 21, dated 3-June-92.)
 * Note: older versions of the IJG code used a zero offset of MAXJSAMPLE/2,
 * rather than CENTERJSAMPLE, for Cb and Cr.  This gave equal positive and
 * negative swings for Cb/Cr, but meant that grayscale values (Cb=Cr=0)
 * were not represented exactly.  Now we sacrifice exact representation of
 * maximum red and maximum blue in order to get exact grayscales.
 *
 * To avoid floating-point arithmetic, we represent the fractional constants
 * as integers scaled up by 2^16 (about 4 digits precision); we have to divide
 * the products by 2^16, with appropriate rounding, to get the correct answer.
 *
 * For even more speed, we avoid doing any multiplications in the inner loop
 * by precalculating the constants times R,G,B for all possible values.
 * For 8-bit JSAMPLEs this is very reasonable (only 256 entries per table);
 * for 12-bit samples it is still acceptable.  It's not very reasonable for
 * 16-bit samples, but if you want lossless storage you shouldn't be changing
 * colorspace anyway.
 * The CENTERJSAMPLE offsets and the rounding fudge-factor of 0.5 are included
 * in the tables to save adding them separately in the inner loop.
 */

#define SCALEBITS	16			/* speediest right-shift on some machines */
#define CBCR_OFFSET	((INT32) CENTERJSAMPLE << SCALEBITS)
#define ONE_HALF	((INT32) 1 << (SCALEBITS-1))
#define FIX(x)		((INT32) ((x) * (1L<<SCALEBITS) + 0.5))

/* We allocate one big table and divide it up into eight parts, instead of
 * doing eight alloc_small requests.  This lets us use a single table base
 * address, which can be held in a register in the inner loops on many
 * machines (more than can hold all eight addresses, anyway).
 */

#define R_Y_OFF		0			/* offset to R => Y section */
#define G_Y_OFF		(1*(MAXJSAMPLE+1))	/* offset to G => Y section */
#define B_Y_OFF		(2*(MAXJSAMPLE+1))	/* etc. */
#define R_CB_OFF	(3*(MAXJSAMPLE+1))
#define G_CB_OFF	(4*(MAXJSAMPLE+1))
#define B_CB_OFF	(5*(MAXJSAMPLE+1))
#define R_CR_OFF	B_CB_OFF	/* B=>Cb, R=>Cr are the same */
#define G_CR_OFF	(6*(MAXJSAMPLE+1))
#define B_CR_OFF	(7*(MAXJSAMPLE+1))
#define TABLE_SIZE	(8*(MAXJSAMPLE+1))


/*
 * Initialize for RGB->YCC colorspace conversion.
 */

METHODDEF void rgb_ycc_start(j_compress_ptr cinfo)
{
	my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
	INT32          *rgb_ycc_tab;
	INT32           i;

	/* Allocate and fill in the conversion tables. */
	cconvert->rgb_ycc_tab = rgb_ycc_tab = (INT32 *)
		(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, (TABLE_SIZE * SIZEOF(INT32)));

	for(i = 0; i <= MAXJSAMPLE; i++)
	{
		rgb_ycc_tab[i + R_Y_OFF] = FIX(0.29900) * i;
		rgb_ycc_tab[i + G_Y_OFF] = FIX(0.58700) * i;
		rgb_ycc_tab[i + B_Y_OFF] = FIX(0.11400) * i + ONE_HALF;
		rgb_ycc_tab[i + R_CB_OFF] = (-FIX(0.16874)) * i;
		rgb_ycc_tab[i + G_CB_OFF] = (-FIX(0.33126)) * i;
		/* We use a rounding fudge-factor of 0.5-epsilon for Cb and Cr.
		 * This ensures that the maximum output will round to MAXJSAMPLE
		 * not MAXJSAMPLE+1, and thus that we don't have to range-limit.
		 */
		rgb_ycc_tab[i + B_CB_OFF] = FIX(0.50000) * i + CBCR_OFFSET + ONE_HALF - 1;
/*  B=>Cb and R=>Cr tables are the same
    rgb_ycc_tab[i+R_CR_OFF] = FIX(0.50000) * i    + CBCR_OFFSET + ONE_HALF-1;
*/
		rgb_ycc_tab[i + G_CR_OFF] = (-FIX(0.41869)) * i;
		rgb_ycc_tab[i + B_CR_OFF] = (-FIX(0.08131)) * i;
	}
}


/*
 * Convert some rows of samples to the JPEG colorspace.
 *
 * Note that we change from the application's interleaved-pixel format
 * to our internal noninterleaved, one-plane-per-component format.
 * The input buffer is therefore three times as wide as the output buffer.
 *
 * A starting row offset is provided only for the output buffer.  The caller
 * can easily adjust the passed input_buf value to accommodate any row
 * offset required on that side.
 */

METHODDEF void
rgb_ycc_convert(j_compress_ptr cinfo, JSAMPARRAY input_buf, JSAMPIMAGE output_buf, JDIMENSION output_row, int num_rows)
{
	my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
	register int    r, g, b;
	register INT32 *ctab = cconvert->rgb_ycc_tab;
	register JSAMPROW inptr;
	register JSAMPROW outptr0, outptr1, outptr2;
	register JDIMENSION col;
	JDIMENSION      num_cols = cinfo->image_width;

	while(--num_rows >= 0)
	{
		inptr = *input_buf++;
		outptr0 = output_buf[0][output_row];
		outptr1 = output_buf[1][output_row];
		outptr2 = output_buf[2][output_row];
		output_row++;
		for(col = 0; col < num_cols; col++)
		{
			r = GETJSAMPLE(inptr[RGB_RED]);
			g = GETJSAMPLE(inptr[RGB_GREEN]);
			b = GETJSAMPLE(inptr[RGB_BLUE]);
			inptr += RGB_PIXELSIZE;
			/* If the inputs are 0..MAXJSAMPLE, the outputs of these equations
			 * must be too; we do not need an explicit range-limiting operation.
			 * Hence the value being shifted is never negative, and we don't
			 * need the general RIGHT_SHIFT macro.
			 */
			/* Y */
			outptr0[col] = (JSAMPLE) ((ctab[r + R_Y_OFF] + ctab[g + G_Y_OFF] + ctab[b + B_Y_OFF]) >> SCALEBITS);
			/* Cb */
			outptr1[col] = (JSAMPLE) ((ctab[r + R_CB_OFF] + ctab[g + G_CB_OFF] + ctab[b + B_CB_OFF]) >> SCALEBITS);
			/* Cr */
			outptr2[col] = (JSAMPLE) ((ctab[r + R_CR_OFF] + ctab[g + G_CR_OFF] + ctab[b + B_CR_OFF]) >> SCALEBITS);
		}
	}
}


/**************** Cases other than RGB -> YCbCr **************/


/*
 * Convert some rows of samples to the JPEG colorspace.
 * This version handles RGB->grayscale conversion, which is the same
 * as the RGB->Y portion of RGB->YCbCr.
 * We assume rgb_ycc_start has been called (we only use the Y tables).
 */

METHODDEF void
rgb_gray_convert(j_compress_ptr cinfo, JSAMPARRAY input_buf, JSAMPIMAGE output_buf, JDIMENSION output_row, int num_rows)
{
	my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
	register int    r, g, b;
	register INT32 *ctab = cconvert->rgb_ycc_tab;
	register JSAMPROW inptr;
	register JSAMPROW outptr;
	register JDIMENSION col;
	JDIMENSION      num_cols = cinfo->image_width;

	while(--num_rows >= 0)
	{
		inptr = *input_buf++;
		outptr = output_buf[0][output_row];
		output_row++;
		for(col = 0; col < num_cols; col++)
		{
			r = GETJSAMPLE(inptr[RGB_RED]);
			g = GETJSAMPLE(inptr[RGB_GREEN]);
			b = GETJSAMPLE(inptr[RGB_BLUE]);
			inptr += RGB_PIXELSIZE;
			/* Y */
			outptr[col] = (JSAMPLE) ((ctab[r + R_Y_OFF] + ctab[g + G_Y_OFF] + ctab[b + B_Y_OFF]) >> SCALEBITS);
		}
	}
}


/*
 * Convert some rows of samples to the JPEG colorspace.
 * This version handles Adobe-style CMYK->YCCK conversion,
 * where we convert R=1-C, G=1-M, and B=1-Y to YCbCr using the same
 * conversion as above, while passing K (black) unchanged.
 * We assume rgb_ycc_start has been called.
 */

METHODDEF void
cmyk_ycck_convert(j_compress_ptr cinfo, JSAMPARRAY input_buf, JSAMPIMAGE output_buf, JDIMENSION output_row, int num_rows)
{
	my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
	register int    r, g, b;
	register INT32 *ctab = cconvert->rgb_ycc_tab;
	register JSAMPROW inptr;
	register JSAMPROW outptr0, outptr1, outptr2, outptr3;
	register JDIMENSION col;
	JDIMENSION      num_cols = cinfo->image_width;

	while(--num_rows >= 0)
	{
		inptr = *input_buf++;
		outptr0 = output_buf[0][output_row];
		outptr1 = output_buf[1][output_row];
		outptr2 = output_buf[2][output_row];
		outptr3 = output_buf[3][output_row];
		output_row++;
		for(col = 0; col < num_cols; col++)
		{
			r = MAXJSAMPLE - GETJSAMPLE(inptr[0]);
			g = MAXJSAMPLE - GETJSAMPLE(inptr[1]);
			b = MAXJSAMPLE - GETJSAMPLE(inptr[2]);
			/* K passes through as-is */
			outptr3[col] = inptr[3];	/* don't need GETJSAMPLE here */
			inptr += 4;
			/* If the inputs are 0..MAXJSAMPLE, the outputs of these equations
			 * must be too; we do not need an explicit range-limiting operation.
			 * Hence the value being shifted is never negative, and we don't
			 * need the general RIGHT_SHIFT macro.
			 */
			/* Y */
			outptr0[col] = (JSAMPLE) ((ctab[r + R_Y_OFF] + ctab[g + G_Y_OFF] + ctab[b + B_Y_OFF]) >> SCALEBITS);
			/* Cb */
			outptr1[col] = (JSAMPLE) ((ctab[r + R_CB_OFF] + ctab[g + G_CB_OFF] + ctab[b + B_CB_OFF]) >> SCALEBITS);
			/* Cr */
			outptr2[col] = (JSAMPLE) ((ctab[r + R_CR_OFF] + ctab[g + G_CR_OFF] + ctab[b + B_CR_OFF]) >> SCALEBITS);
		}
	}
}


/*
 * Convert some rows of samples to the JPEG colorspace.
 * This version handles grayscale output with no conversion.
 * The source can be either plain grayscale or YCbCr (since Y == gray).
 */

METHODDEF void
grayscale_convert(j_compress_ptr cinfo, JSAMPARRAY input_buf, JSAMPIMAGE output_buf, JDIMENSION output_row, int num_rows)
{
	register JSAMPROW inptr;
	register JSAMPROW outptr;
	register JDIMENSION col;
	JDIMENSION      num_cols = cinfo->image_width;
	int             instride = cinfo->input_components;

	while(--num_rows >= 0)
	{
		inptr = *input_buf++;
		outptr = output_buf[0][output_row];
		output_row++;
		for(col = 0; col < num_cols; col++)
		{
			outptr[col] = inptr[0];	/* don't need GETJSAMPLE() here */
			inptr += instride;
		}
	}
}


/*
 * Convert some rows of samples to the JPEG colorspace.
 * This version handles multi-component colorspaces without conversion.
 * We assume input_components == num_components.
 */

METHODDEF void
null_convert(j_compress_ptr cinfo, JSAMPARRAY input_buf, JSAMPIMAGE output_buf, JDIMENSION output_row, int num_rows)
{
	register JSAMPROW inptr;
	register JSAMPROW outptr;
	register JDIMENSION col;
	register int    ci;
	int             nc = cinfo->num_components;
	JDIMENSION      num_cols = cinfo->image_width;

	while(--num_rows >= 0)
	{
		/* It seems fastest to make a separate pass for each component. */
		for(ci = 0; ci < nc; ci++)
		{
			inptr = *input_buf;
			outptr = output_buf[ci][output_row];
			for(col = 0; col < num_cols; col++)
			{
				outptr[col] = inptr[ci];	/* don't need GETJSAMPLE() here */
				inptr += nc;
			}
		}
		input_buf++;
		output_row++;
	}
}


/*
 * Empty method for start_pass.
 */

METHODDEF void null_method(j_compress_ptr cinfo)
{
	/* no work needed */
}


/*
 * Module initialization routine for input colorspace conversion.
 */

GLOBAL void jinit_color_converter(j_compress_ptr cinfo)
{
	my_cconvert_ptr cconvert;

	cconvert = (my_cconvert_ptr) (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, SIZEOF(my_color_converter));
	cinfo->cconvert = (struct jpeg_color_converter *)cconvert;
	/* set start_pass to null method until we find out differently */
	cconvert->pub.start_pass = null_method;

	/* Make sure input_components agrees with in_color_space */
	switch (cinfo->in_color_space)
	{
		case JCS_GRAYSCALE:
			if(cinfo->input_components != 1)
				ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
			break;

		case JCS_RGB:
#if RGB_PIXELSIZE != 3
			if(cinfo->input_components != RGB_PIXELSIZE)
				ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
			break;
#endif							/* else share code with YCbCr */

		case JCS_YCbCr:
			if(cinfo->input_components != 3)
				ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
			break;

		case JCS_CMYK:
		case JCS_YCCK:
			if(cinfo->input_components != 4)
				ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
			break;

		default:				/* JCS_UNKNOWN can be anything */
			if(cinfo->input_components < 1)
				ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
			break;
	}

	/* Check num_components, set conversion method based on requested space */
	switch (cinfo->jpeg_color_space)
	{
		case JCS_GRAYSCALE:
			if(cinfo->num_components != 1)
				ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
			if(cinfo->in_color_space == JCS_GRAYSCALE)
				cconvert->pub.color_convert = grayscale_convert;
			else if(cinfo->in_color_space == JCS_RGB)
			{
				cconvert->pub.start_pass = rgb_ycc_start;
				cconvert->pub.color_convert = rgb_gray_convert;
			}
			else if(cinfo->in_color_space == JCS_YCbCr)
				cconvert->pub.color_convert = grayscale_convert;
			else
				ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
			break;

		case JCS_RGB:
			if(cinfo->num_components != 3)
				ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
			if(cinfo->in_color_space == JCS_RGB && RGB_PIXELSIZE == 3)
				cconvert->pub.color_convert = null_convert;
			else
				ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
			break;

		case JCS_YCbCr:
			if(cinfo->num_components != 3)
				ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
			if(cinfo->in_color_space == JCS_RGB)
			{
				cconvert->pub.start_pass = rgb_ycc_start;
				cconvert->pub.color_convert = rgb_ycc_convert;
			}
			else if(cinfo->in_color_space == JCS_YCbCr)
				cconvert->pub.color_convert = null_convert;
			else
				ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
			break;

		case JCS_CMYK:
			if(cinfo->num_components != 4)
				ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
			if(cinfo->in_color_space == JCS_CMYK)
				cconvert->pub.color_convert = null_convert;
			else
				ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
			break;

		case JCS_YCCK:
			if(cinfo->num_components != 4)
				ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
			if(cinfo->in_color_space == JCS_CMYK)
			{
				cconvert->pub.start_pass = rgb_ycc_start;
				cconvert->pub.color_convert = cmyk_ycck_convert;
			}
			else if(cinfo->in_color_space == JCS_YCCK)
				cconvert->pub.color_convert = null_convert;
			else
				ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
			break;

		default:				/* allow null conversion of JCS_UNKNOWN */
			if(cinfo->jpeg_color_space != cinfo->in_color_space || cinfo->num_components != cinfo->input_components)
				ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
			cconvert->pub.color_convert = null_convert;
			break;
	}
}
